1. Field of the Invention
This invention relates generally to a prosthetic eye, and, more particularly to an improved ocular replacement apparatus that provides for integrated coupling of a prosthesis to an implant using magnetic attraction.
2. Description of the Related Art
There are instances where an eye has become damaged due to trauma or disease wherein it is necessary to remove the entire eyeball from the eye cavity. Thereafter, a prosthetic eye may be replaced in the eye cavity: to provide a cosmetically acceptable appearance; to reduce the psychological trauma associated with loss of an eye; and/or to correct any medical problems associated with the loss of an eye.
Presently, the most accepted medical procedures for the removal of a diseased natural eye is to perform either an enucleation or an evisceration. Generally, enucleation involves first sedating the patient and anesthetizing the eye. The attaching ocular muscles and tissues are then dissected completely away from the patient's diseased natural eyeball. The conjunctiva and Tenon's capsule are incised down to the sclera as close as possible to the cornea. The extra ocular muscles are disinserted at the point of their insertion on the sclera. The optic nerve is severed and the natural eyeball is removed. While controlling bleeding, a porous plastic or coral ball-shaped implant is inserted into the eye cavity. Thereafter, the ocular muscles are sutured to the exterior, porous surface of the implant, or a homologous or autologous material wrap, in accordance with their correct anatomical positions. Once muscle attachment is completed, the Tenon's capsule and conjunctiva are closed up over the implant.
There are some instances where it is desirous to perform an evisceration rather than an enucleation of the eye. Evisceration can be performed for treatment of a blind painful eye if a rapid, less traumatic surgery, as compared to enucleation. In particular, evisceration may be desirable for old or very ill patients in whom general anesthesia is a risk. Generally, evisceration involves undermining the conjunctiva with scissors that the sclera around the limbus is free of conjunctiva. A keratome entry through the limbus into the anterior chamber of the eye is performed and curved corneal scissors is used to excise the entire cornea. An evisceration spoon is used to remove the intraocular contents while the globe is fixed by holding onto the limbal sclera with toothed forceps. Thereafter, the scleral shell is opened with forceps and the uveal tissue is scraped from inside the eye using a gauze square held in a hemostat. Bleeding is controlled by cautery. The implant can then be inserted within the cavity and, thereafter, the scleral shell is closed. The ocular muscles remain in tact and, in most cases, the patient has full mobility of the ocular globe.
In either an enucleation or an evisceration, the patient is measured for a cosmetic prosthesis after a healing period of approximately two months. After another four to six months, the prosthesis is integrated with the implant. At present, the most common method to fully integrate the prosthesis with the implant involves the use of a coupling post. To fit the post to the implant, the conjunctiva is incised and pulled partially apart to expose an anterior portion of the implant. A hole is then drilled approximately 5-7 mm deep into the implant, perpendicular to the anterior surface. The coupling post is then inserted and anchored within the hole so that an exposed end portion of the post protrudes approximately 2 mm beyond the conjunctiva. The conjunctiva is then pulled closed around the base of the post over the anterior surface of the implant. A hole or other means on the inner surface of the prosthesis receives the protruding end of the post so that the prosthesis remains attached to the post. Hence, as the muscles of the eye move the implant, the coupling post serves to move the prosthesis with the implant to simulate natural eye movement.
While the above-described procedure is the most effective method presently known to couple a prosthesis to an eye implant, patients have experienced numerous problems with this technique. Specifically, fully integrated prosthetic implant devices have been disappointing in the past because of associated complications, such as extrusion of the implant and conjunctival erosion. In some instances, movement of the prosthesis and coupling post relative to the conjunctiva has caused extreme irritation to the conjunctiva tissue, resulting in infection and rejection of the implant.
In the past, others have proposed use of magnets to achieve coupling of the prosthesis to the implant. Examples of this can be found in the U.S. patents to Rosen, et al., U.S. Pat. No. 2,661,480 and Morrell, U.S. Pat. No. 2,637,043, as well as the Soviet Union patent to Riga, U.S. Pat. No. 633,525. One of the major problems encountered with these coupling systems, as well as similar magnetic coupling arrangements proposed in the past, is excessive pressure between the prosthesis and implant due to the magnets being disposed in direct axial alignment. It has been discovered that too much pressure on the eye tissue may cause tissue breakdown, which eventually may lead to infection, tissue dehiscence, or implant extrusion. These past attempts using implants with magnets disposed in direct axial alignment have never been successful. This is due largely to the fact that the excessive attraction resulting from the direct axial alignment of the magnets causes too much pressure on the conjunctiva.
There is a further problem encountered when magnets are used in the implant. In particular, it has been found that magnets, when embedded within the human body, loose their attracting abilities within approximately one year. This has been particularly proven in the use of magnets in dental implants, which are covered by mucosa tissue in the mouth, similar to the tissue found in the eye socket. Once the magnets loose their magnetically attractive characteristics, it is necessary to remove the implant to replace the magnets. This is especially a problem with orbital implants. Because the muscles and tissue become attached to the implant, major invasive surgical procedures are necessary to remove and replace the implant in the eye cavity. Once the orbital implant has become connected to the muscles, and the tissue has attached to the surface of the implant, major surgery is required to remove the implant from the eye cavity. Accordingly, it has been discovered that the use of magnets in the orbital implant is not desirable due to their limited useful life.
Accordingly, there is an urgent need in the art for an improved ocular replacement system and method to more effectively couple a prosthesis to an eye implant in a manner which reduces the likelihood of irritation, infection and/or rejection of the implant and which avoids the need for subsequent surgical invasive procedures.